Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$59.34	10.777%	$65.7351	$65.74	$65.75	$65.70
Purchase #2	$164.90	9.821%	$181.0948	$181.09	$181.10	$181.10
Purchase #3	$202.40	9.795%	$222.2251	$222.23	$222.25	$222.20
Purchase #4	$52.27	9.770%	$57.3768	$57.38	$57.40	$57.40
Purchase #5	$47.62	13.826%	$54.2039	$54.20	$54.20	$54.20
Purchase #6	$52.26	13.446%	$59.2869	$59.29	$59.30	$59.30
Purchase #7	$141.82	5.664%	$149.8527	$149.85	$149.85	$149.90
7 purchase totals =	$720.61		$789.7753	$789.78	$789.85	$789.80